The present invention relates to a package, which accommodates electronic parts as typified by a crystal resonator or a piezoelectric element.
Because a crystal resonator has an excellent characteristic in frequency, it is often used as a device, more specifically, as one of the components to be mounted on a printed substrate. However, in order to stabilize the characteristic of the crystal resonator, it is desirably placed within a closed housing for shutting off the influence by outside air. An example of such a package structure has been proposed in “Garasu-Seramikku Fukugotai oyobi Sorewo Mochiita Furatto Pakkeji Gata Atsuden Buhin (Glass-Ceramic Composite and Flat Package Type Piezoelectric Parts Using The Same)” (which will be called Patent Document 1).
According to Patent Document 1, a package in which a quartz piece is accommodated in a base member and is covered with a cap member is characterized in that the package is formed by a material having a substantially equal coefficient of thermal expansion to that of the quartz piece. That is, the package is made of ceramics with a mix of glass powder.
However, because the package according to Patent Document 1 is made of a glass-ceramic composite, it is manufactured by using single part production in which a quartz piece is mounted on one base member and is covered with a cap member, which may significantly lower the productivity. In addition, the glass-ceramic composite is difficult to process, which may increase the production cost.
In order to overcome the drawback, methods that manufacture the package from easy-processable glass have been disclosed, and an “electronic-parts package” (refer to Patent Document 2), for example, has been disclosed.
With reference to FIGS. 6A to 6F, the outline of Patent Document 2 will be described where FIGS. 6A to 6F correspond to steps (a) to (f), respectively. According to Patent Document 2, a method has been proposed which produces an electronic-parts package 100 through a step (a) of forming a through-hole on a base member 110, a step (b) of pouring low-melting glass to the through-hole and inserting a metal pin 120 thereto, a step (c) of squeezing the metal pin 120 thereinto and processing the glass plate to a concave shape, a step (d) of forming an electrode 130 by printing, a step (e) of mounting parts 140 such as a crystal resonator to the metal pin, and a step (f) of sealing a cap member 160 and the base member 110 through a sealing agent 150. Among them, in the step (c), the glass is welded at the heating temperature equal to or higher than the softening point temperature (approximately 1000° C.) of glass so that the metal pin 120 can be sealed to the base member 110. Therefore, the airtightness can be certainly kept in the step (f), which allows the production at low costs.    [Patent Document 1] JP-A-11-302034    [Patent Document 2] JP-A-2003-209198
The step (c) of the manufacturing method for the electronic-parts package 100 has a problem shown in FIGS. 7A to 7C. That is, because, as shown in FIG. 7A, the metal pin 120 is covered by the low-melting glass 170 when the metal pin 120 is short or is squeezed thereinto less, the electric connection between the metal pin 120 and the electrode 130 formed in the step (d) may not be obtained. Furthermore, as shown in FIG. 7B, even when the metal pin 120 is squeezed thereinto as designed, the base member 110 is exposed to the temperature equal to or higher than the softening point. Therefore, there is concern that the glass may cover the tip of the metal pin 120. There is still another problem that, as shown in FIG. 7C, because the metal pin 120 is exposed to a temperature of approximately 1000° C., an oxide film 180 may grow around the metal pin 120, which may bring the electrode 130 and the electronic parts 140 out of conduction.